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Space-inspired A simple urine test could soon reveal more about a person's bones than x-rays, say US researchers after publishing results of an early phase study funded by NASA.

The technique could help astronauts cope with the bone loss that can occur in weightless environments like space, but may also have broad implications for people who suffer from osteoporosis or cancers that may spread to the bones.

"Right now there aren't very good ways to detect bone loss before there has already been a fair amount of bone loss," says senior author Dr Ariel Anbar, a professor at Arizona State University (ASU).

"This is something new that we are developing. This is not a technique they (NASA) have worked with before so they have invested in our research to see if there is a better or complementary way to address their issues," says Anbar.

The method measures calcium isotopes, which are essentially atoms of an element that differ in mass. These isotopes are present in a person's urine and serve as an indicator of bone strength based on the balance of minerals.

The study measured bone loss in a dozen healthy volunteers who participated by agreeing to sustained periods of bed rest over the course of 30 days.

Bed rest is a condition which mirrors weightlessness in space and can lead to bone loss.

The new test could detect bone loss in as little as 10 days after the bed rest began.

"Bone is continuously being formed and destroyed," says co-author Dr Jospeph Skulan, an adjunct professor at ASU who devised the mathematical model for predicting calcium isotope ratios in blood and urine.

"In healthy, active humans, these processes are in balance. But if a disease throws the balance off then you ought to see a shift in the calcium isotope ratios."

Still years away

Patients did not need to submit to x-rays, nor did they digest any artificial tracers so they were not exposed to radiation.

But while this "proof of concept" study was simple for the patient, the mass spectrometry methods used for the analysis were more complicated, and it would likely take years of research before the test may reach the public, says Anbar.

"The paper suggests an exciting new approach to the problem," says Rafael Fonseca, chair of the Department of Medicine at the Mayo Clinic in Arizona.

Fonseca is a specialist in multiple myeloma, a type of cancer which can destroy the bones, and was not involved in the study but is working with the authors on collaborative research based on its findings.

"Right now, pain is usually the first indication that cancer is affecting bones. If we could detect it earlier by an analysis of urine or blood in high-risk patients, it could significantly improve their care," says Fonseca.